The present invention relates generally to gas turbine technology and, more specifically, to the design of a gas turbine diffuser exhaust frame.
A gas turbine engine is conventionally configured to receive ambient air and to discharge exhaust or combustion gases into an annular diffuser. The combustion gases are then discharged to atmosphere through a conventional exhaust stack.
The engine may take any conventional form including single or dual rotor engines, with one or more compressors, followed in turn by a combustor, (or an annular array of combustors) in which compressed air is mixed with fuel and ignited for generating the combustion or exhaust gases. Disposed downstream of the one or more combustors are one or more turbine stages which extract energy from the exhaust gases for powering the engine as well as typically providing output power through an output shaft for a load such as a generator.
The diffuser or exhaust frame typically includes an annular frame having an inner annular wall spaced radially inwardly from an outer annular wall or casing which define radially therebetween an annular flow channel for channeling the combustion gases to the diffuser and exhaust stack. The frame also typically includes a plurality of circumferentially-spaced and aligned, radially-extending struts disposed between the inner and outer annular casings.
In current gas turbine exhaust frame designs, a single row of rectangular struts are used to transfer loads from the inner to the outer annular members. The shape of each strut, and its cross-sectional area, are governed by the shape of an airfoil that surrounds the strut, and the total load to be transferred. In this type of configuration, the airfoils are relatively long, thereby producing larger losses, especially during part-load operating conditions.
It would therefore be desirable to have a strut/airfoil arrangement which enables smaller cross-sectional areas, and which produces smaller performance losses especially at part-load conditions.